Polymerization of perhalocarbons with trifluorodichloropropionyl peroxide



April 5, 1955 A. L. DITTMAN ET POLYMERIZATION OF PERHALocAQoNs WITH2305306 TRIFLU R D Filed y 51 O O ICHLOROPROPIONYL PEROXIDE 3Sheets-Shet 1 0 0.0] 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.|O 0.IICONCENTRATION OF TRIFLUORODICHLOROPROPIONYL PEROXIDE FIG. I

2a +sgc :9 $5 0 0 0.0l 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.l0 O-llCONCENTRATION OF TRIFLUORODIGHLOROPROPIONYL PEROXIDE INVENTQRS FIG 2ALBERT L. DITTMAN 1mm m. WRIGHTSON B as" M April 5, 1955 Filed May 11,1951 YIELD A. L. DITTMAN ETAL POLYMERIZATION OF PERHALOCARBONS WITHTRIFLUORODICHLOROPROPIONYL PEROXIDE 3 Sheets-Sheet 2 O 5 IO l5 TEMPJ'C(WITH TRIFLUORODICHLOROPIONYL PEROXIDE) FIG. 3

5 O 5 IO I5 TEMP. C (WITH TRIFLUORODIGHLOROPIONYL PEROXIDE) INVENTORSFIG. 4 ALBERT L. DITTMAN JOHN M. WRIGHTSON %ORNEY United States PatentCfilice 2,705,706 Patented Apr. 5, 1955 POLYMERIZATION OF PERHALOCARBONSWITH TRIFLUORODICHLOROPROPIONYL PEROXIDE Albert L. Dittman, Jersey City,N. J., and John M. Wrightson, Whittier, Calif., assignors to The M. W.Kellogg Company, Jersey Ci N. J., a corporation of Delaware ApplicationMay 11, 1951, Serial No. 225,850 2 Claims. (Cl. 26092.1)

mally liquid and solid polymers of this monomer.

This invention is a continuation-in-part of our prior and copendingapplication Serial No. 98,276, now U. S. Patent No. 2,636,908, filedJune 10, 1949; and is also a continuation-in-part of our prior andcopending application Serial No. 157,268, filed April 21, 1950, in whichwe are co-inventors With Cscar A. Blum.

Normally liquid and solid perhalocarbons have been produced by thepolymerization of a monomer in the presence of certain promoters, and,in the case of liquids, also in the presence of a chain-transfersolvent.

For example, under suitable conditions of temperature and residencetime, and in the presence of trichloroacetyl peroxide,trifluorochloroethylene can be polymerized to obtain chemically andphysically stable, solid polymers having a variety of uses. Benzoylperoxide has been employed to produce liquid polymers. The disadvantagesof these promoters in comparison with the promoters of the presentinvention, resides in their being more expensive to produce, and inbeing unstable at relatively high temperatures. In the case of benzoylperoxide, there is the further disadvantage that the fragments ofpromoter attached to the polymer contain hydrogen which makes thepolymer less stable.

It is, therefore, an object of the present invention to polymerizeperhalo-olefins under suitable conditions in the presence of a newpromoter to produce perhalo-polymers.

Another object of the invention is to provide an improved method forproducing perhalo-olefin polymers of predetermined chemical and physicalcharacteristics and high yields.

Still another object of the invention is to provide an improved methodfor producing polymers of trifluorochloroethylene.

A further object of the invention is to provide a novel promotersuitable for use in the polymerization of perhalo-olefins to produceperhalo-polymers.

A still further object of the invention is to provide a method forproducing a novel promoter suitable for use in the polymerization ofperhalo-olefins to produce perhalo-polymers.

Various other objects and advantages of the present invention willbecome apparent to those skilled in the art from the accompanyingdescription and disclosure.

As herein employed, perhalocarbons are defined as compounds consistingsubstantially exclusively of carbon and halogen with any degree ofunsaturation and containing only negligible amounts of other elements,such as hydrogen and oxygen, in a quantity less than about 2 weight percent as impurities. These other elements are derived from materialsutilized in the process as will hereinafter become apparent.Perhalo-olefins are defined as perhalo-olefins having any degree ofunsaturation, and consisting of halogens and carbon. Perfluoro-olefinsare defined as perhalo-olefins having any degree of unsaturation andconsisting of fluorine and carbon.

Perfluorochloro-olefins are defined as perhalo- 8 olefins consisting offluorine, chlorine and carbon. The preferred perfluorochloro-olefins ofthis invention are those containing not more than one chlorine atom percarbon atom.

According to this invention, perhalo-olefi-ns are homo' under suitablepolymerization conditions in the presence of a halogenated acylperoxide, viz., trifluorodichloropropionyl peroxide as a nature ofthermal plastics, in high yields with good selectivity for the desiredproduct.

The perhalo-olefins which may be homopolymerized or copolymerized inaccordance with the process of the invention include perfluoro-olefinsand perfluorochloroolefins, such as trifluorochloroethylene,tetrafluoroethylene, perfluorobutadiene, difluorodichloroethyleneincluding both CF2=CC12 and CFC1=CFC1, perfluoropropene,periluoromonochloropropene, perfluorobutene, per-fluoromonochlorobutene,diphenyldifluoroethylene, etc. Typical examples of copolymerization ofthe above perhalo-olefins include the copolymerization oftrifiuorochloroethylene and fiuorochloroisobutene; oftrifluorochloroethylene and diphenyldifiuoroethylene; oftrifluorochloroethfiuorobutadiene and perfluorostyrene, etc.

The term polymerization includes, in its broadest sense, bothhomopolymerization and copolymerization of the perl1alo-olefins withother compounds. In instances where homopolymerization is sought to becarried out, as much as 5 per cent of a comonomer, which does notnecessarily affect the characteristics of the product, but which is usedas a modifier, may be present.

Diphenyldifluoroethylene, useful for efiecting the aforementionedcopolymerization with trifluorochloroethylene may be prepared by thefollowing series of re- In Equation I, following, chloral Was reactedwith hydrogen fluoride and mercuric oxide, in accordance with theindicated stoichiometrical requirements, to obtain monochlorodifluoroacetaldehyde.

Equation I chloral monoehlorodifluoro acetaldehyde The aqueous mixtureof monochlorodifluoro acetaldehyde, separated from the product recoveredin Equation I, above, was next reacted, according to Equation II,following, with benzene, according to the indicated stoichiometricalrequirements, in the presence of sulfuric acid as a catalyst to producediphenyldifluorochloroethane.

The melting point of the above-mentioned diphenyldifluorochloroethaneproduct was found to be 42 C.

aroaroc The following analytical data were obtained for this compound:

Chlorine Mol. Wt. Content Found 248. 2 15. Theoretical 252. G 14. 04

Equation HI diphenyldifluoro ethylene chloroethane The above-mentioneddehydrochlorination reaction was continued until the theoreticalrequirement of chlorine (Cl-) was produced along with a heavy oil. Thisoil was distilled through a small unpacked column at 0.3 mm. to obtain amajor fraction boiling between about 75 C. and about 85 C.

In the polymerization of trifluorochloroethylene, to which thisinvention has particular application, to produce either normally liquidor solid perhalo-polymers, the promoter employed is a major factor inefiec-ting the polymerization and determining the molecular weight,yield and characteristics of the product produced. According to theinvention, as indicated above, polymerization or copolymerization ofperhaloolefins is carried out in the presence of a halogenated acylperoxide, viz., triiluorodichloropropionyl peroxide, as a promoter.

The concentration of trifluorodichloropropionyl peroxide, used as apromoter in accordance with the process of the invention, is importantin determining the molecular weight, yield and characteristics of theproduct produced. in the case of producing normally solid polymers ofthe nature of thermoplastics, the amount of promoter used usually variesbetween about 0.01 and about 0.5 weight per cent of the monomer in thereaction mixture, depending upon the molecular weight of the ultimateproduct to be produced. in the case of producing normally liquid andwaxy polymers, the amount of promoter used varies between about 0.5 andabout weight per cent of the monomer in the reaction mixture, with apreferred range between about 2 and about 6 weight per cent of themonomer in the reaction mixture.

in general, it has been observed when producing polymers employing theaforementioned trifluorodichloropropionyl peroxide as a promoter, anincrease in the amount of promoter used, within the aforementioned rangeof concentrations, results in a decrease of the molecular weight of theresulting product. In the case of the solid plastic produced, the N. S.T. value is proportional to the molecular weight and thereforeindicates, relatively, the molecular weight of the polymer produced. TheN. S. T. value is defined as the no-strength-temperature of the solidpolymer.

A. no-strength-temperature (N. S. T.) between about 200 C. and about 350C. is characteristic of a normally solid polymer, produced in accordancewith the present process, having plastic characteristics. The mostdesirable plastic characteristics of the normally solid polymer areobserved at N. S. T. values between about 240 and about 350. Theno-strength-temperature (N. S. T.) is determined in the followingmanner:

A sample of polytrifiuorochloroethylene is hot pressed into a hick sheetand is cut into a strip of /8 x x 1%". This strip is notched /s" fromthe top of the strip so that the dimension at the notch is x A fine wireand a standard weight is attached to one end of the strip. The weight ofthe solid polymer plus the wire and standard weight shall equal /2 gram.The strip is then attached in a furnace and fixed vertically therein.The temperature surrounding the sample inside the furnace is increasedat a rate of about 1 /2 C. per minute in the furnace as the breakingtemperature is approached. The no-strength-temperature is the breakingtemperature of the sample. Differences of about 5 C. are consideredsignificant.

In producing normally solid polymers, in accordance with the presentprocess, and since the trifluorodichloropropionyl peroxide promoter maybe solid under normal conditions and substantially insoluble in themonomer, a solvent is usually employed to dissolve the promoter. The useof the promoter in the form of a solution facilitates handling andintimate admixture of the promoter with the monomer in the reactionzone. Preferred solvents are those which are non-reactive and have aboiling point higher than the boiling point of the monomer. The quantityof solvent containing the promoter, is usually between about 1 and about20 per cent of the monomer feed, however larger or smaller amounts maybe used without departing from the scope of the invention. A preferredsolvent is trichloroiluoromethane. The solution of the promoter ismaintained at a sutiiciently low temperature prior to introduction intothe reaction zone in order to minimize decomposition.

When producing normally liquid and waxy polymers, in accordance with thepresent process, the polymerization of the monomer is also carried outin the presence of a chain-transfer solvent. The amount ofchain-transfer solvent used varies between about 20 and about per centof the monomer in the reaction mixture. In general, an increase in theamounts of chain-transfer solvent results in a iower molecular weight orN. S. T. value of the resulting product of polymerization. A preferredchaintransfer solvent is chloroform, although other chaintransfersolvents may also be employed including carbon tetrachloride,bromotrichloromethane, trichlorotrifluoroethane,1,2,2-tetrachloroethane, ethylene and saturated halogenated aliphaticcompounds, in general, preferably containing bromine or chlorine.

The trifiuorodichloropropionyl peroxide may be prepared by first formingtrifiuorodichloropropionyl chloride (CFsCClzCOCl).Trifluorodichloropropionyl chloride is prepared by bubbling chlorine andoxygen through trifiuorotrichloropropene (CFzCCl=CCl2) in the presenceof actinic radiation, (for example, ultra-violet light) to producetrifluorodichloropropionyl chloride, as a liquid.

Liquid tritiuorodichloropropionyl chloride thus produced, is nextreacted with sodium peroxide (NazOz) sus: pended in aqueous sodiumchloride solution (20% by weight of sodium chloride) to yield thedesired trifluorodichloropropionyl peroxide. The quantity oftrifiuorodichloropropionyl chloride reacted with sodium peroxide is inaccordance with stoichiometric requirements, although excesstrifluorodichloropropionyl chloride may also be used. The reaction iscarried out at a temperature in the range between about 20 C. and about0 C, and preferably at a temperature of about -16 C., in an open mixingvessel at atmospheric pressure. Reaction takes place almostinstantaneously.

The peroxide (trifluorodichloropropionyl peroxide) is recovered from thereaction mixture by extraction withFreon-11(trichloromonofiuoromethane). The peroxide crystallizes when theFreon solution is cooled to about 70 C. and "is purified by washing andrecrystaliizing in fresh Freon-l1. The purified peroxide is thendissolved in Freon-11 and diluted to the desired concentration forpolymerization.

The following examples will serve to illustrate the method for thepreparation of trifiuorodichloropropionyl peroxide of the presentinvention.

EXAMPLE I 21.6 grams of trifiuorodichloropropionyl chloride (which is3.4 grams in excess of the stoichiometric quantity) was reacted with 3,3grams of sodium peroxide suspended in 248 grams of sodium chloridesolution (20% sodium chloride by weight) at 16 C. The above reactionproduced a yield of 10.3, grams of trifluorodichloropropionyl peroxide.

, -16 C grams of trifluorodichloropropionyl peroxide.

EXAMPLE n As previously indicated, the homopolymerization orcopolymerization of the perhalo-olefin in the presence of the promoteris carried out under suitable conditions of product. For the productionof a plastic polymer, a temperature between about -20 C. and about 150C. is employed, depending upon the particular promoter and otheroperating conditions employed. The preferred temperature is betweenabout 20 C. and about 25 C. At a temperature between about 5 C. andabout C. trifluorodichloropropionyl peroxide is preferably employed inan amount between about 0.01 and about 0.02 per cent of the monomer inthe reaction mixture. The pressure employed should in any case be atleast in excess of the vapor pressure of the monomer at thepolymerization temperature employed.

hen polymerization is eflected under liquid phase conditions to producea normally liquid or waxy polymer, a temperature between about 0 C. andabout 300 C. is employed, depending upon the particular chain-transfersolvent and operating conditions employed. A temperature between about70 C. and about 200 C. is preferred. A sufiiciently high pressure at thetemperature of polymerization to maintain liquid phase conditions isemployed. Excess pressures over those necessary to obtain liquid phaseconditions may also be used, ranging as high as 15,000 to 30,000 poundsper square inch gage.

The residence time any particular polymerized monomer is retained in thepolymerization zone. waxy polymers, the residence time to be allowed forcompleting the reaction and obtaining the desired product and yield,will range from a matter of seconds to as much as 100 hours, preferablybetween about 1 minute and about 10 hours. The time of polymerization orresidence time will eifect both yield and molecular weight of theproduct. However, after a minimum residence time for a giventemperature, the effect of continued residence time is less pronouncedand does not become a major factor. For example, at a temperaturebetween about 0 C. and about C. a minimum residence time of about 24hours is required. For the production of a solid plastic polymer, longerperiods of residence time are preferred and may range from a matter ofminutes to about 8 days.

The use of inert diluents, such as water or hydrocarbon oils, in thepolymerization reaction mixture as a means for heat removal andotherwise assuring a smoother reaction, is within the scope of theinvention. In indicating concentrations of promoter and monomer, thepresence of such d' uents is not considered in reporting percentages,but only the presence of the active 1ngredients, such as monomer,promoter and chain-transfer solvent are considered.

Control of the concentrations may be accomplished by continuous orintermittent addition of the active components of the polymerizationreaction as they are consumed or converted, in an amount sutficient tomaintain their concentration substantially constant or within thepreferred range. In the case of producing normally solid or plasticpolymers, the promoter is consumed more rapidly than the monomer.Therefore, the promoter is added at a more rapid rate than the monomer,in continuous operations. In the production of normally liquid polymers,the monomer and promoter are consumed more rapidly than thechain-transfer solvent. Therefore, both monomer and promoter are addedmore rapidly than the chain-transfer solvent during a continuouspolymerizais defined as the length of time i For the production ofliquid or i tion process, in order to maintain their concentration atthe desired value.

Figures 1 and 2, graphically illustrating the results ob tained overperiods of 24 hours, indicate that the yield of polymer formed from themonomer trifluorochloroethylene, in accordance with the present process,is proportional to and the N. S. T. is inversely proportional to theperoxide concentration, employing trifluorodichloropropionyl peroxide,as the promoter. it will be noted that the lower concentrations of theperoxide are much more efficient in producing high N. S. T. polymer. Anincrease in the peroxide concentration of 13.5 times, will increase thepolymer yield only about 3 times. The

curves in these graphs also indicate the ease with which high yields ofthe polymer, having N. S. T. values be tween about 250 and about 275 C.can be obtained.

Figures 3 and 4 of the drawings, illustrate the effect of temperature onthe efficiency of the peroxide promoter for a given period of time incarrying out the poly merization of trifiuorochloroethylene as amonomer, in accordance with the present process. It will be noted thatfor a 24 hour period, the optimum temperature is about 10 C. The N. S.T. temperature relationship is complicated by the initial formation oflow molecular weight polymers. The N. S. T. value is inverselyproportional to the polymerization temperature. It will be noted fromthe curves in Figure 3 that the polymerization temperature has far lesseffect on the N. S. T. value than on the yield of polymer formed.

Figures 5, 6 and 7 tionship between N. S. T. value, yield,

promoter is the same in each case, to produce polymers oftrifluorochloroethylene in accordance with the process of the presentinvention. The curves in Figure 7 indicate the eifect of temperature inreducing the low initial rate of polymerization. The curves in Figure 5indicate the sharp increase in N. S. T. valuei which is proportional tothe yield of polymer pro duce From the above data it will be seen thatyields of trifluorochloroethylene polymer from about 15 to about 40 percent, having N. S. T. values between about 250 C. and about 300 C., canbe obtained in a period of 24 hours, by employing temperatures betweenabout 10 C. and about 20 C. to carry out the polymerization reaction, inthe presence of trifiuorodichloropropionyl peroxide promoter.

Various modifications of the aforementioned process of the inventionwill be apparent to those skilled in the art, without departing from thescope of the invention.

We claim:

1. A process for preparing a plastic trifluorochloroethylene-polymerwhich comprises: polymerizing trifiuorochloroethylene at a temperaturebetween about 20 C. and about 25 C., in the presence oftrifiuorodichloropropionyl peroxide as a promoter, for a time sufficientto produce a plastic polymer of trifiuorochloroethylene; and maintainingthe concentration of the promoter between about 0.01 and about 0.5 percent of trifluorochloroethylene in the reaction mixture.

2. A process for preparing perhalo-polymers which comprises:polymerizing a perhalofiuoro-olefin in which the halogens are selectedfrom the group consisting of chlorine and fluorine under conditions oftemperature and residence time, and in the presence oftrifluorodichloropropionyl peroxide as a promoter, to produce a polymerof the perhalo-olefin as a product of the process.

References Cited in the file of this patent

1. A PROCESS FOR PREPARING A PLASTIC TRIFLUOROCHLOROETHYLENE POLYMERWHICH COMPRISES: POLYMERIZING TRIFLUOROCHLOROETHYLENE AT A TEMPERATUREBETWEEN ABOUT -20*C. AND ABOUT 25*C., IN THE PRESENCE OFTRIFLUORODICHLOROPROPIONYL PEROXIDE AS A PROMOTER, FOR A TIME SUFFICIENTTO PRODUCE A PLASTIC POLYMER OF TRIFLUOROCHLOROETHYLENE; AND MAINTAININGTHE CONCENTRATION OF THE PROMOTER BETWEEN ABOUT 0.01 AND ABOUT 0.5 PERCENT OF TRIFLUOROCHLOROETHYLENE IN THE REACTION MIXTURE.